This proposal is a competing renewal application. The focus during the initial funding period was on the relationship of dietary intake of long chain n-3 polyunsaturated fatty acids from seafood with primary cardiac arrest (PCA). The investigators now propose to extend the population-based, case-control study to determine whether the dietary intake of trans- fatty acids derived from partially hydrogenated unsaturated fatty acids measured through a biomarker are directly associated with the risk of primary cardiac arrest. Cases of PCA who were attended by paramedics in King County, Washington will be identified. Demographically similar controls will be identified from the same community using random digit dialing. Blood specimens from both previously identified and newly identified cases (collected by paramedics in the field) and controls will be analyzed for red cell membrane total trans-fatty acid levels. This serves as a biomarker of dietary trans-fatty acid intake. Spouses of subjects will be interviewed to obtain information on usual saturated fat intake, recent changes in diet and other risk factors. Additionally, among spouses of newly identified subjects, the types of fat used in cooking and as spreads will be assessed. Analyses will focus on the relationship between red cell membrane total trans-fatty acid levels and the risk of PCA after adjusting for saturated fat intake and other risk factors. The investigators also plan to extend a detailed diet substudy in a subset of control subjects to confirm the relationship between the dietary intake of trans-fatty acids and red cell membrane levels and evaluate whether the relationship is independent of other nutrients.